The invention relates to the field hydraulic excavators or mini-excavators having hydraulically operated earth-moving tools.
On FIG. 1 is depicted a conventional excavator 10. It comprises an upper frame 11 carrying the excavator's superstructure 12 which comprises an operator station which can be enclosed in a closed cabin 14 and an engine arrangement which may be located in a rearwardly located engine compartment 16. Some excavators do not have such closed cabin and have an operator station which can be totally open or only covered by a canopy. The upper frame carries the machine's main work equipment: a digging assembly 18. Typically, the digging assembly 18 can have a boom 20 which is pivotably connected around a horizontal axis on the upper frame. The boom 20 can be lowered and lifted vertically by a boom cylinder 22. At the free end of the boom 20, an arm 24 may be pivotably connected around another horizontal axis, and it can be lowered and lifted by an arm cylinder 26. At the free end of the arm 24, a working tool, such as bucket 28, is pivotably connected around another horizontal axis and it can be pivoted relative to the arm 24 by a bucket cylinder 30. The digging assembly 18 as a whole can usually be rotated with respect to the upper frame around a vertical axis A1, thanks to a non represented hydraulic cylinder.
The work equipment of such excavators is most often controlled through one or several manually operated hydraulic pilot valve units. For the digging equipment 18 of an excavator, it is most often provided two hydraulic joystick controllers which the operator can operate by hand. These controllers are located preferably on both sides of an operator seat, near the front end of the seat. In some machines, such controllers are arranged on the seat armrests, in a more affordable design, the controllers can be arranged directly on a platform which forms the supporting structure of the operator station.
A lower frame carries the undercarriage 32 of the machine 10, which comprises mainly the drive train 34 of the machine. In the example shown, the drive train is in the form of a pair of endless tracks but it could also be made of a set of wheels. It is common for such a construction machine to be designed as a skid steer machine. Is such a case, the drive train comprises at least two propulsion units, one dedicated to the right side of the machine and the other one dedicated to the left side of the machine. Each propulsion unit therefore drives one endless track (left or right) or a set of synchronous wheels located on one side of the machine. In many cases, the propulsion units are hydraulically powered, and they are piloted through a dedicated hydraulic pilot circuit. The controllers comprise each at least one manually operated proportional valve which provides oil pressure to one side or the other of the propulsion unit's power hydraulic circuit, at a varying pressure and/or flow rate. In a conventional design, the manually operated valves for controlling the propulsion units are arranged at the floor level of the operator station, right in front of the driver, and can be operated manually by hand, through a substantially vertically extending lever portion of the pilot valve unit and/or by foot through a pedal portion. A single 4-axis controller can also be used for independently controlling the two propulsion units.
In the example shown, the undercarriage 32 also comprises a working tool which is for example in the form of a front blade 36. For this blade to be perfectly convenient, it may be desirable that it not only is capable of being lowered and lifted with respect to the undercarriage but also that it can be rotated around a horizontal axis and/or around a vertical axis. As it is well-known, the superstructure 12 of the machine can swivel around a vertical axis with respect to the undercarriage thanks to a suitable mechanical link 15 between the upper frame and the lower frame, with the possibility of both frames rotating with respect to each other around a vertical axis. In many cases, the superstructure can swivel 360 degrees, thanks to a swivel joint 15.
Most construction equipment machines use a hydraulic pressure system to operate the various working tools 28, 36 carried by the machine, as well as to operate the drive train 34. The hydraulic pressure system comprises at least one hydraulic pump which feeds pressurized fluid to various actuators through hydraulic circuits comprising hydraulic lines, distributors, valves, etc. The hydraulic pump is driven by the engine arrangement, which can comprise a Diesel engine and/or an electric motor.
The majority of parts of the hydraulic pressure system are usually located on the upper frame of the machine. On the other hand, some of the tools carried by the machine may be located on the lower frame, such as the blade 36 mentioned above, not to mention the fact that the drive train, carried of course by the lower frame, usually comprises two hydraulic motors and, possibly, a hydraulic actuated gearbox.
Therefore, the machine is equipped with a rotary joint which provides hydraulic passages which permit the hydraulic lines to pass from the upper frame to the lower frame without being interrupted and without impeding the free swiveling of the two frames. Therefore, the rotary joint may have an upper part connected to the upper frame and a lower part connected to the lower frame. The upper and lower parts of the rotary joint have for example respective annular contact surfaces bearing one against the other, and at least one of the annular contact surfaces comprises an annular groove which is closed by either a corresponding annular groove on the other contact surface, or simply closed by that other contact surface. The groove(s) define an annular fluid flow path at the interface between the parts of the rotary joint. An upper portion of a hydraulic line (for example a hose or a pipe) is connected to the upper part of the rotary joint while a lower portion of the hydraulic line (made for example of another hose or pipe) is connected to the lower part of the rotary joint, both being fluidly connected to the annular groove. With this construction the upper and lower portions of the hydraulic line are fluidly connected one to the other irrespective of the angular position of the two parts of the rotary joint.
Conventionally, the operator station comprises a platform which is arranged on top of the frame 11. The platform is preferably attached to the frame through suspension systems. The platform, which can be made of one or several parts, typically forms the floor of the operator station and can also form a seat support, side consoles and even controller consoles. Therefore, the platform is not necessarily flat. Typically, a good portion of the hydraulic circuit of the machine is located on top of the frame 11, but below the platform. On the other hand, the various hydraulic pilot controllers are obviously at least partly received on top of the platform so as to be accessible to the driver.
Up to now such controllers are simply fixed on top of the platform in some way and are then connected to the rest of the hydraulic circuit through flexible pipes. In an assembling process, most of the hydraulic circuit is first mounted on the frame, and the platform is subsequently attached on top of the frame. The controllers are then subsequently attached on the platform, or may have been attached to the platform prior to assembly on the frame. In both cases, this means that the connection between the controllers and the rest of the hydraulic circuit has to be performed after the platform has been assembled on top of the frame. This has well known disadvantages. For example, it is frequently quite complicated to perform such connection of the controllers, because of lack of accessibility. Also, such assembly process makes it impossible to test the hydraulic pilot circuit, for example for leaks, before the assembly of the platform. If an hydraulic component is found to be defective, it may be necessary to disassemble the platform to provide some remedy, but such disassembly of the platform necessitates a prior disconnection of the pilot circuit from the hydraulic distribution system so that it is not any more possible to operate the hydraulic circuit for diagnosing purposes.
Therefore, the invention has the goal to provide a new design of an excavator which allows an easier assembly and disassembly of the hydraulic circuit assembly. The invention also has the goal of allowing a new assembling process and a new disassembling process for an excavator.
In view of this goal, the invention provides for an excavator comprising at least:                a frame.        a platform on top of the frame,        a hydraulic circuit assembly including at least:        a main pump delivering pressurized fluid        a number of hydraulic actuators        a hydraulic distribution system for distributing pressurized fluid from the main pump to the various hydraulic actuators according at least to a hydraulic pilot circuit comprising at least one manually operated hydraulic pilot valve unit connected to the hydraulic distribution device,        
and wherein:                the hydraulic distribution system is received on top of the frame but below the platform, while the pilot valve unit is at least partly received on top of the platform,        the pilot valve unit is hydraulically connected to the hydraulic distribution system subassembly by hydraulic pipes;        the platform comprises a dedicated hole capable of receiving therethrough at least that pan of the pilot valve unit which is received on top of the platform;        the pilot valve unit is fixed, directly or indirectly, on the platform such that the unit, or the hydraulic pipes extend through the hole;        
characterized in that the pilot valve unit can be mounted from below the platform, through the dedicated hole, and is fixed on the platform from above the platform.
The invention also provides for a process for assembling such an excavator, characterized, in that the process includes at least:                the step of preassembling the hydraulic distribution system on the frame, and of hydraulically connecting the pilot valve unit to the hydraulic distribution stem so that no further hydraulic connection is needed;        the subsequent step of placing the platform on top of the frame, including passing at least part of the pilot valve unit through a dedicated hole in a platform.        the subsequent step of fixing, from above the platform, the pilot valve unit directly or indirectly on the platform.        
The invention also provides for a process for disassembling the platform from the frame of such an excavator, characterized in that the process includes at least                the step of releasing, from above the platform, the pilot valve writ from the platform;        the subsequent step of removing the platform from the frame, including passing at least part of the pilot valve unit through a dedicated hole in a platform without necessarily disconnecting the pilot valve unit from the hydraulic distribution system.        